1. Field of the Invention
The present invention relates to a zinc oxide eugenol cement composition which is used in dentistry as the temporary sealing material having an anodyne, sedative and antiphlogistic effect upon oral disease and the temporary cementing material for restorations such as clowns and bridges.
2. Statement of the Prior Art
The temporary sealing and cementing materials are indispensable for ordinary dentistry, and are used for the purpose of, e.g., temporary sealing for the sedation of cavities after the elimination of dental caries, temporary cementing of temporary crowns after pier tooth preparation, and temporary sealing for medicaments in endodontics. The temporary sealing material is generally classified into the following three types.
(1) Temporary stopping composed mainly of gutta-percha, PA1 (2) Hydraulic temporary sealing material, and PA1 (3) Zinc oxide eugenol cement. PA1 (1) it has a good marginal sealing effect upon the margin of a cavity, PA1 (2) it is easily removable in detachment, and PA1 (3) it set within a short time. PA1 (a) Base Agent (Liquid) Component PA1 (b) Setting Agent (Powder) Component PA1 (a) Base Agent (Paste) Component PA1 (b) Setting Agent (Paste) Component
The temporary stopping is thermoplastic, and is put on the market in the bar or pellet form. In use, this is softened by heating, and is pressed in a tooth cavity for temporary sealing. Due to its simplicity, such a stopping method has been used for many years. With this material, however, there is left much to be desired in view of the marginal sealing effect, since it shrinks largely when cooled and set, so that its adherence to a tooth is insufficient.
The hydraulic temporary sealing material also leaves much to be desired in view of the marginal sealing effect, since it takes a long period of time (several hours) for setting, and produces only an insufficient bonding strength to a tooth.
The requirements of the temporary sealing material are that:
Since the zinc oxide eugenol cement meets all the requirements, excels in flowability, and has suitable degrees of strength and bonding strength, it is frequently used as the temporary cementing material. The zinc oxide eugenol cement is supplied in the form of (1) a combination of a powdery setting agent containing zinc oxide with a liquid base agent containing eugenol, and (2) a combination of a tube in which a setting agent containing zinc oxide in a highly flowable pasty state with a tube in which a base agent containing eugenol in a highly flowable pasty state.
In use, the setting and base agents are mixed together for temporary sealing or cementing use. Such mixing are mainly carried out by a dental assistant.
The time needed to finish mixing of the setting and base agents varies depending upon the skill of operators, and has a great influence upon the performance of the set product, since there is a difference in the dispersed state between both agents. Especially when mixing a liquid base agent containing eugenol with a powdery setting agent containing zinc oxide, the powdery component is divided into three equal portions which are to be successively mixed with the liquid component to the desired consistency. Since the powders scatter vigorously, however, difficulty is encountered in the incorporation thereof into the liquid component, and a relatively long time of 1 to 2 minutes is required for mixing. Depending upon mixing skill, there are differences in the dispersed state achieved by mixing and in the time needed to finish mixing, which have a remarkable influence upon the workability of temporary sealing and cementing and the bonding strength. Thus, the zinc oxide eugenol cement is a material-difficult-to-handle, for which a dental assistant or hygienist in charge of mixing is required to have skill. If the eugenol-containing base agent and the zinc oxide-containing setting agent each are in the form of a highly flowable paste, it is then relatively easy to force that paste out of the tube by equal length onto a mixing pad for mixing. However, it is likely that such a paste may leak out of the tube in use or storage and pollute a clinic room, giving out a strongly irritating eugenol odor. Thus, the zinc oxide eugenol cement is a material which is difficult for an operator to handle. The set product is also relatively soft so that it wears away due to biting or brushing, thus offering a deformation or disengagement problem.
As mentioned above, as long as the zinc oxide-containing setting agent and the eugenol-containing base agent are used in the powder-to-liquid form or paste-to-paste form, as is the case with the prior art, difficulty would be still encountered in mixing thereof, and a leakage problem difficult to solve would be likely to arise in use and storage.